fix issue related to reloading

important points to note:

* never explicitly require services, just like how we dont explicitly do `require 'doctor'` to access `Doctor` model. This is important for rails reloading to work.
* for folders like `app/services` you can follow conventions that we follow for controllers. you can call `DoctorFinderService` instead of `Services::DoctorFinder`
* as mentioned in https://github.com/rails/rails/issues/14382, scope `DoctorFinder` under `Services`, just like how we dont scope models under `Models`. Reason being, `services` is top level folder just like `models` folder